There isn't a lot of reviews on these earphones outside of amazon.com, so hopefully mine will get some attention. I would have killed for a thorough write-up like this when doing my research on these... oh well.

Brief background
I bought these with the intention of using them solely at work for listening in th office, watching movies on the slow days, and for general fairly quiet environments. I didn't buy them to use on a construction site or at a race track so I wasn't expecting miracles with regards to noise cancellation.

I felt, that after reading a couple reviews online that these were a good alternative to the high-priced Bose Quiet Comfort series both in terms of sound AND comfort for 1/3 of the price. Apparently The New York Times thought so too.

First impressions & total usage
Comes in a nice sturdy, plush case. Nice zipper compartment inside to store the extra plugs. Single cabled to the left ear cup.

Right out of the box these headphones are/were very comfortable. Very. The leather is extremely soft and hugs your ears nicely without clamping onto your head. Panasonic really got this area right, these are every bit as comfortable as the Bose. Even now, after 5 months of use, they are still very comfortable.

The build is solid, the plastic is of average quality and seems durable enough. The cups rotate flat for convenient storage in it's case.The cups also pivot nicely to conform to different sized heads. The top of the overhead band is nicely padded with 'Panasonic' written on the top. The headband only really only touches the very top of your head and doesn't mash your hair down on all sides, FYI. I get about 25-30 hours on a single AAA battery.

BLUE LED light indicates on.

There is a simple ON/OFF switch on the Left earcup to turn the noise cancelation on. The headphones still work with noise cancellation turned off. This was one of the stupidest things Bose did, you can't turn the NC off while still listening, and when the battery dies - the music dies on the Bose. There are times when I want to hear music in the office but still want to hear if someone walks up behind me and starts talking, or the phone rings, and I don't need 92% of the sound zapped away...

Features and sound quality
Panasonic claims 92% noise cancellation and I would say they are pretty darn close. I don't have dB level testing to prove this, but when the NC is turned on, everything else around you just shuts up. Now. I got to play with the Audio Technica ATH-ANC7 in the Apple store and the Panasonics embarrass those in comfort and noise canceling. The Panasonics provide far superior noise canceling than the ANC7, the ANC7 provide about 3/4 the amount of canceling than the HC500. Not to mention, the ANC7 felt stiff, hard, and uncomfortable compares to the HC500's. When you turn the NC on, there is a slight, slight "hiss" sound coming from the NC. It faintly sounds like putting a sea shell to your ear. It's there when there is nothing playing, but quickly disappears when music plays.

The sound produced from these is not bad, but it's not mind blowing either. You're not going to drop your jaw or have an "eargasm" over these. It's probably just personal preference (because I tend to like my tunes more "warm" and heavier on the low end, not "flat" by any means) but for my tastes these were just a little flat. Sure the bass is there, but there wasn't enough of it. Only a couple times did I ever hit the low, low boomy notes and that was on some Pendulum tracks.

The mids are equally recessed, and do not come across as "in your face". I wish they were more lush and deep but that is just personal preference. The mids, however, are not lumped into the bass and are easily distinguished. These are pretty decent for male vocals especially. John Mayer, David Gilmour, Jack Johnson, etc.

The highs are clear and crisp, but not the most crisp I've ever heard. Again, there is nothing to gripe about in this category, it's just not awe inspiring. I never felt like anything was muffled, even while watching DVDs on the PC I could hear every background noise, every breath, every crash on the movies. Female vocals like Sheryl Crow, Stevie Nicks, and Amy Winehouse sound good, not great.

I feel like I have to crank up the volume to higher levels just to get the full experience from these phones. By "high volumes" I'm talking level 16 or 17 on a 40 scale on my i7.

The fit is good and covers most of my large ears. The isolation is good as well, better than my Audio Technica ATH-ES7. I would attribute this to the smooshy leather pads being so plush.

Final notes
These Panasonics are like the unsung hero in the field of mid-range noise canceling headphones. Bigger names like Audio Technica and Bose will always garner more attention and a loyal following. While there is nothing glaringly wrong with these, there is nothing glaringly awesome about these. What you're left with is a very comfortable headphone that cancels noise extremely well, that sounds about average. For some, this is just what they're looking for. For others, like me, it just wasn't warm enough for my liking. Like I said, there's nothing wrong with them, they're just not my cup of tea.

New cable (left) compared to original cable (right).
Original cable is 5' in length.

Oh, my cat promptly chewed through the stock cable after having these 1 week so I bought a thicker, "upgraded" Belkin cable that is very nice. It doesn't make a world of difference in terms of sound but it looks nice paired with the grey in the phones. The stock cable is VERY thin.

In closing, I would say for the money $100 (+/-) these would be a great set of headphones for 85% of the people. The other 15% that don't like their music flat, but prefer juicy mids and thick bass are probably better off looking else where unless comfort is your main deciding factor.